1. Field of the Invention
The invention lies in the telecommunications field. More specifically, the invention relates to a base station, a mobile station and a method for data transmission in a communications system, in particular in a CDMA mobile radio system, with the data being transmitted in structured form in frames in such a manner that it is possible for a mobile station to carry out other functions, in particular to carry out measurements via a receiving device, during one or more interruption phases in which it interrupts the reception (of the previous source or of the data of the base station) and/or the processing of received data or the sending process. In the following text, the term xe2x80x9ctransmissionxe2x80x9d also means sending and/or receiving.
In communications systems, data (normally voice data, image data or system data) are transmitted on transmission paths between base stations and mobile stations. In radiocommunications systems, this is done using electromagnetic waves via an air or radio interface. In the process, carrier frequencies are used which are in the frequency band provided for the respective system. In the case of GSM (Global System for Mobile Communications), the carrier frequencies lie in the neighborhood of 900 MHz. For future radiocommunications system, for example the UMTS (Universal Mobile Telecommunications System) or other third-generation systems, the frequencies provided are in the frequency band around 2000 MHz.
Particularly in future CDMA systems, transmission from the base station is essentially continuous in the downlink direction, for example, that is to say in the direction from a base station to a mobile station. The data transmitted during the sending process are normally structured into frames, which each have a predetermined length. Particularly in the case of different services, such as voice data transmission and video data transmission, the frames may also have a different structure and length. The structure and/or length of each frame in a continuous sequence of frames is, however, predetermined and/or is identified by the mobile station.
Particularly in cellular mobile radio systems, the mobile station occasionally has to carry out functions other than data reception as well, which cannot be carried out at the same time, at least when only a single receiving device is being operated. For example, the mobile station in a cellular radiocommunications system in which the base stations in different cells transmit at different frequencies, it is necessary to carry out measurements from time to time to determine whether the mobile station can receive radio signals with good reception quality from another base station. For this purpose, the mobile station sets its receiving device to a frequency other than the frequency at which it is currently receiving data.
In order to be able to send from the base station to the mobile station without any interruption, it has already been proposed for the mobile station to be equipped with a second receiving device. However, this solution is generally rejected in practice, for cost reasons.
Another proposal is known, on the basis of which the base station interrupts the sending process at predetermined times in order to allow the receiving station to carry out an adjacent channel search (search for an adjacent base station or for specific data packets transmitted from these base stations which, in the following text, is also intended to mean synchronization, frequency-correction or pilot-signal bursts) via its single receiving device.
In order to avoid data loss, the base station initially sends the data at a higher transmission rate than the essentially constant continuous transmission rate. To avoid this leading to higher bit error rates (BER), the transmission power must also be increased during this time.
The frequency at which the interruption phases recur and the length of the interruption phases depend on the respective system and also on the respective operating mode of the system. For example, interruption phases each having a length of 5 to 6 ms are sufficient for an adjacent channel search by a mobile station in a cellular-organized radiocommunications system. In systems with an HCS (Hierarchic Cell Structure), it is sufficient to carry out an interruption phase approximately every 100 ms. Since the reduction in the transmission quality also increases with the number of interruption phases inserted, it is desirable to insert as few interruption phases as possible.
The object of the present invention is to provide a method for data transmission of the above-mentioned type, a mobile station, and a base station which overcome the above-noted deficiencies and disadvantages of the prior art devices and methods of this general kind, and which allow monitoring of second base stations while maintaining good transmission quality.
With the above and other objects in view there is provided, in accordance with the invention, a method for data transmission in a mobile radio system, which comprises:
transmitting data between a first base station and a mobile station using a first transmission method;
during specific transmission phases, inserting interruption phases wherein the mobile station interrupts a transmission of data and the mobile station is switched to receive data packets from a second base station using a second transmission method; and
depending on a reception result, sending information influencing an insertion of the interruption phases from the mobile station to the first base station.
In an alternative embodiment of the novel method, the method steps include:
transmitting data in structured form in frames from a first base station to a mobile station;
during specific transmission phases, inserting interruption phases wherein the mobile station interrupts at least one process selected from the group consisting of receiving data and processing received data, and the mobile station is switched to receive data packets from a second base station; and
depending on a reception result, sending information influencing the insertion of interruption phases from the mobile station to the first base station.
In a further variation, there is provided a method of transmitting data in a mobile radio system, which comprises:
transmitting data in structured form in frames from a mobile station to a first base station;
during specific transmission phases, inserting interruption phases wherein the mobile station interrupts the transmission of data, and wherein the mobile station is switched to receive data packets from a second base station; and
depending on a reception result, sending information influencing the insertion of interruption phases from the mobile station to the first base station.
With the above and other objects in view there is also provided, in accordance with the invention, a mobile station, comprising:
means for transmitting data from and to a first base station using a first transmission method;
means, connected to said transmitting means, for inserting pauses at least during specific transmission phases, in which a transmission of data is interrupted;
means for switching to reception of data packets sent from a second base station using a second transmission method;
means for determining a reception result relating to the data packets; and
means, connected to said determining means, for sending information to the first base station, and to therewith influence an insertion of interruption phases as a function of the reception result of the mobile station.
Alternatively, there is provided a mobile station, comprising:
means for receiving data sent in structured form in frames from a first base station;
means for inserting pauses, at least during specific reception phases, during which one of a reception and processing of received data is interrupted;
means for switching a reception of data packets sent from a second base station;
means for determining a reception result relating to the data packets; and
means for sending information to the first base station, and to therewith influence an insertion of interruption phases as a function of the reception result of the mobile station.
There is also provided, in accordance with the invention, a mobile station, comprising:
means for transmitting data sent in structured form in frames to a first base station;
means for inserting pauses, at least during specific transmission phases, during which a transmission of data is interrupted;
means for switching to receiving data packets sent from a second base station;
means for determining a reception result relating to the data packets; and
means for sending information to the first base station, and to therewith influence an insertion of interruption phases as a function of the reception result of the mobile station.
There is also provided a base station, comprising:
means for transmitting data from and to a mobile station;
means, connected to said transmitting means, for inserting interruption phases at least during specific transmission phases;
means, connected to said inserting means, for receiving information influencing an insertion of the interruption phases; and
means, connected to said receiving means, for influencing the insertion of interruption phases as a function of a reception result of the mobile station.
In the alternative, there is also provided, a base station, comprising:
means for sending data in structured form in frames to a mobile station;
means, connected to said sending means, for inserting interruption phases, at least during specific transmission phases;
means, connected to said inserting means, for receiving information influencing an insertion of the interruption phases; and
means, connected to said receiving means, for influencing the insertion of interruption phases as a function of a reception result of the mobile station.
In accordance with a concomitant feature of the invention, a novel base station comprises:
means for receiving data in structured form in frames from a mobile station;
means for inserting interruption phases at least during specific reception phases;
means, connected to said inserting means, for receiving information influencing an insertion of the interruption phases; and
means, connected to said inserting means, for influencing the insertion of interruption phases as a function of a reception result of the mobile station.
The invention is accordingly based on the idea of sending information, which influences the insertion of interruption phases, from the mobile station to the first base station depending on a reception result which is obtained during the interruption phases, in which the receiving device is switched to receive data packets from the second base stations.
The data packets sent from the second base station may also be data packets (synchronization data packets) which are to be detected or characteristic data packets (frequency-correction data packets).
The expression influencing the insertion of interruption phases also means restricting the number of future interruption phases and/or ending the insertion of interruption phases and/or controlled continuation of the insertion of further interruption phases and/or controlling the duration of the interruption phases.
The expression xe2x80x9cthe mobile station is switched to receive data packetsxe2x80x9d in the context of this application also means that, after the conventional analog and digital filtering and, possibly, derotation, the received data packet is compared with the correlation sequence corresponding to the training sequence (for example is correlated with it), and a search for data packets is thus carried out. Other methods may also be used instead of correlation (for example FIR, IRR or other filters). If a data packet is received or is detected with adequate quality, or the information transported by means of the data packet is determined with adequate quality, etc., then it is possible to speak of a positive reception result for this data packet.
Thus, while, for example, data are transmitted in the downlink direction from a first base station to a mobile station using a first transmission method, interruption phases are inserted at least during specific transmission phases, in which interruption phases the mobile station interrupts the reception of the data sent from the first base station and/or the processing of the received data, and in which interruption phases the mobile station is switched to receive data packets which are sent from a second base station using a second transmission method. Depending on a reception result relating to these data packets sent from a second base station, information which influences the insertion of interruption phases is sent from the mobile station to the first base station.
A first transmission method which is used by a first base station may in this case be a CDMA method, and a second transmission method, which is used by a second base station, may be a GSM method. Thus, for example, in order to monitor GSM base stations, interruption phases are inserted in a UMTS transmission. In order to reduce the number of these interruption phases once sufficient information for the adjacent channel search has been received, a message is transmitted from the mobile station to the UMTS base station in order to influence or restrict the insertion of further interruption phases.
It is thus possible to end the insertion of interruption phases as early as possible, and thus to restrict them as much as possible, as soon as sufficient information relating to the second base stations to be monitored is known, and thus to improve the transmission quality.
In one design variant of the invention, once a characteristic data packet has been received, no more interruption phases are inserted after reception of a following data packet which is to he detected.
It is thus possible to keep the number of interruption phases that need to be inserted low by using the known frame structure of the data transmission from the second base station to the mobile station.
Another development variant of the invention provides for the mobile station to be switched to receive data packets from a number of base stations and, depending on the reception results, for information which influences the insertion of the interruption phase to be sent to the first base station.
This means that a number of adjacent base stations can be monitored successively, and that the insertion of interruption phases can be ended for the time being as soon as they have been monitored to a sufficient extent.
A further refinement of the invention provides for the information for influencing the insertion of the interruption phases, and information relating to the second and/or third base stations, to be transmitted by means of the same message.
This allows adjacent base stations to be monitored, and information relating to the observation results to be transmitted, with as little signaling complexity as possible.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for data transmission in a mobile radio system, a mobile station and a base station, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.